1. Technical Field
This invention relates generally to image capture devices having optical zoom capabilities, and more particularly to an image capture device having an electronically switchable optical zoom capability that can change an image magnification without lens movement relative to an image sensor.
2. Background Art
People today are taking more pictures. Advances in technology have made this possible. Prior to the advent of digital photography and digital cameras, a person wanting to take a picture of a friend had to invest in expensive cameras, professional lenses, several rolls of film, and costly film processing. Today, however, digital cameras fit into a pocket and enable people to take pictures more effortlessly.
When purchasing a camera, photographers often prefer cameras with some type of zoom magnification capability. A “zoom” camera is simply one that is capable of changing a magnification of an image. In the world of digital photography, zoom capability comes in one of two forms: digital zoom and optical zoom.
In an optical zoom system, mechanical motors and gears within the camera move the lens element relative to the film or image sensor to adjust the focal length of the system. The space between the lens elements and the film or image sensor changes, thereby altering the optical magnification of the system. By contrast, in a digital or electronic zoom system, the lens elements remain stationary at a physically fixed distance relative to image sensor. Image magnification is altered by blowing up and cropping a subsection of an image. As such, the user sees only a portion of the image. Digital zoom reduces the number of pixels used to generate the stored image. Photo enthusiasts generally prefer optical zoom systems due to their higher quality images. Digitally magnified images often appear grainy and sometimes look out of focus, as less data is used for an equally sized, zoomed image.
Optical zoom systems are problematic for small electronic devices. A first problem is that they are mechanical in nature, requiring substantial space for many moving parts. Even in a small optical zoom system, the lens elements may have to move across a range of tens of millimeters to cover a 2 to 1 or 3 to 1 magnification range. In small, handheld devices, such as mobile phones and the like, there is often insufficient space for the motors, lens motion assemblies, and other components that are required. For this reason alone, conventional optical zoom systems have traditionally been too large and fragile for handheld electronic devices such as mobile telephones.
Next, optical zoom systems are slow. In conventional mechanical optical zoom systems, such as those found in traditional 35 millimeter cameras, it may take a time of several hundred milliseconds to several seconds to alter the magnification by physically moving the lens relative to the image sensor and then reacquiring focus. When a child takes his first steps, parents may find themselves disappointed to miss such a memorable event because of delay caused by the optical zoom system.
Third, optical zoom systems rely on motors and gears. These motors and gears are mechanical components, and are therefore subject to wear. Continued wear can lead to component failure.
There is thus a need for an improved optical zoom system for compact portable electronic devices.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve understanding of embodiments of the present invention.